Synchronizers for motor vehicle manual transmissions are known in various forms, both with and without locking devices. With the so-called single-cone synchronizer (known under the Applicant's designation ZF-B), a coupling element comprises a friction cone, which is placed in contact with an opposite cone on a synchronizer ring in order to balance the different speeds of the transmission shaft and the idler gear to be engaged. While the single-cone synchronizer comprises only a single friction pair, the known double-cone synchronizer (known under the Applicant's designation ZF-D) comprises a double-cone ring with tapered surfaces arranged parallel relative to one another. Thus two friction pairs are used, which serves to reduce the shifting force and increase the friction momentum capacity. The drawback of the double-cone synchronizer is that it requires narrower manufacturing tolerances and thus leads to higher manufacturing costs.
Also known is the so-called locking pin synchronizer, in which two synchronizer rings, each with one inner and one outer cone, mesh with idler gears in order to balance the speeds. The synchronizer rings are equipped with locking pins around their outer circumference, which are held in borings in a synchronizer sleeve. Further details on these known synchronizers may be found in the technical literature, for example, G. Lechner and H. Naunheimer, Fahrzeuggetriebe [Motor Vehicle Transmissions], 1994, Springer Publishers, pp. 225-260.
A further locking pin synchronizer was disclosed in EP 0 492 836 B1, wherein the synchronizer rings each comprise an outer cone, which functions in a non-positive connection with an opposite cone on the idler gears. One disadvantage of this known design is an increased shifting force and a reduced amount of transmittable torque.
The object of the present invention is to achieve a reduced shifting force with increased friction momentum in a synchronizer of the type described above without increasing manufacturing costs.